993 Head Studs

[1972_911T]

Steve do you have any knowledge or opinion on the casper labs delivar studs that have recently been listed in the pelican catalogue?

Steve

[Steve@Rennsport]

Originally Posted by 1972_911T

Steve do you have any knowledge or opinion on the casper labs delivar studs that have recently been listed in the pelican catalogue?

Steve

I have no experience with them.

Given whats at stake and my potential liability for the customer, I will stick with the factory ones since they have been quite successful.

I would only try them on a shop engine for a few years before we risk them on a customer's engine.

[cnavarro]

No, I meant like a stock 930 or 964/993 cylinder where the stud bosses are cast in and inbetween the fins are closed off to keep the cooling air from reaching the studs, versus earlier cylinders where the studs are exposed to the cooling air.

I have had customers use the dilivar 911 studs on the 356 with our cylinders, but I was curious about how the elements might affect the dilivar or promote the hydrogen imbrittlement problem.

[Steve@Rennsport]

Originally Posted by cnavarro

No, I meant like a stock 930 or 964/993 cylinder where the stud bosses are cast in and inbetween the fins are closed off to keep the cooling air from reaching the studs, versus earlier cylinders where the studs are exposed to the cooling air.

I have had customers use the dilivar 911 studs on the 356 with our cylinders, but I was curious about how the elements might affect the dilivar or promote the hydrogen imbrittlement problem.

I would have no grief on the use of late Dilavars in all of them with the exception of Biral cylinders since I don't think they need them.

I see no issues with Dilavars on the 356 and have never experienced a failure due to hydrogen embrittlement,......

[cnavarro]

Good to know. Can you post the part numbers for the correct dilivar studs then, for posterity's sake so when someone is searching threads they can find the right stud?

[J P Stein]

The part # is lost in time for me, but here's a pic. These were the latest & greatest at the time.

[Steve@Rennsport]

Here you go:

993.101.170.51 (These are used on the TT, RS, and RSR engines)

[WERK I]

Originally Posted by Steve@Rennsport

Here you go:

993.101.170.51 (These are used on the TT, RS, and RSR engines)

These are the studs I selected and installed on my rebuild. If they're good enough for 993 TT with over 500HP, that's good enough for me.
After over 6K miles and 2 1/2 years of use, no problems whatsoever.

[Roslin]

I used the 993 Dilavar studs in the lower row in my SC rebuild last winter.

My philosophy was following : I have heard that some of the very high tensile race studs, needs re-torque ? - i do not want this at all ! second, i heard that these studs could come lose because of the thermal expansion of the engine.
third, why would Porsche continue with the Dilavar technology, if they was so bad ??

What is the worst thing - a lose head stud or a broken one ...and what
will maybe appear first ??

Some pictures

[hhlodge]

Originally Posted by Steve@Rennsport

Here you go:

993.101.170.51 (These are used on the TT, RS, and RSR engines)

I am just jumping on this thread. My stock 1991 965 is about to get all new studs as one was broken when they went in to see the cause of some leaks at the valve covers. Would you folks suggest they use these (or other) factory Dilivars? Also, the car has almost 60K miles. Should I have them do valves and guides while they are in there? I don't want to do more than I need. Hell, the car seemed to run fine and only went in for a suspected bad alternator.

[blue72s]

Did you see this month's (Dec) Excellence mag about BA's comments on head studs (page 46)? :

Eventually, Porsche switched back to steel head studs for all types of air-cooled 911 engines. I was at the factory in December of 1997, which was right at the end of air-cooled production. At that time, Porsche was making 996, Boxster, 993, and 993 Turbo engines side-by-side on the assembly line. While I was there, I noticed that two different styles of steel studs were being used for the air-cooled engines. I knew they were steel because I was carrying a magnetic money clip and I was able to check them by hand. Remember, Dilavar is a non-ferrous material, and magnets will not stick to it. The first stud style was a steel design similar to those used on early 911s. The others were what we call "all-thread" studs (though there is a non-threaded area in the middle of these studs). It looked to me like the all-thread studs were being used on naturally-aspirated 993 engines, and the plain design was reserved for Turbo applications.

[WERK I]

When I rebuilt my engine over two years ago, I contacted Hendrick Porsche and ordered a full set of 993TT head studs. The studs I received were the full threaded type described by BA above.

[p930t]

The full treaded type is the 993 TT original Porsche, using Dilavar material.
Even if they are Dilavar they must not be compared to the old studs used from .... 1975( i beleive) and also used in my 1978 Turbo which had 18 out of 24 studs broken after long term storage.

If you ask RUF or any other major european professional engine tuner what they use you will find that they most probably use the full treaded original 993TT studs and not aftermarket studs. There is a reason for this.

I am using the 993TT studs for my rebuild even if it by far is the most expensive option.

[911 tweaks]

so, what is the conclusion on the "new" currently available 993TT studs:
1 are they steel or dilavar?
2. is there a space in the middle of the stud, as BA said, that is NOT threaded?
3. are they epoxy/or something coated?
4. should the readers here use this stud for ALL rebuilds or just the turbo rebuilds?
5. IF 2 different studs recommended, what stud for which applications? (one for turbo the other for all other applications?)
***HOPEFULLY THE EXPERTS CAN CHIME IN TO SET THIS SUBJECT TO REST...if that is possible***
Bob

[P.R]

Hi,

You can replace your studs with the standard studs that the factory began using in 1984 ( 3,2l engine ), they are cheap and they do not fail like the ones on the 3,0l engine.

The 993,101,170,51 is very nice but they are expensive, I have bought 24 of them for my 3,0l race engine but I believe that the 3,2l studs would have done the job as good as the "993" studs.

I will go for the 3,2l studs next time.

Regards/ P.R

[Henry Schmidt]

Supertec head studs are the only head studs that are designed with modern engineering concepts.
The Supertec stud offers more threads at the case end (the deeper into the case you go the better the structural integrity) highest quality SS and hardware that is superior to anything Porsche offers for this purpose. The head nut are 12 point, serrated flange, fine thread for positive grip and smoother, more accurate torquing. The washers are hardened and ground.
This 12 point nut also offers the clearance necessary for twin plug conversions.
We also offer a life time warranty. They will never break, you have my word on it.
The best thing is that they are offered directly for our host.

[911 tweaks]

Hi Henry, can you comment on 2 items and how your product addresses these please:
1. possible "loosening nut" concerns requiring re torqueing at future intervals
2. thermal expansion concerns of the rod material... how does your metal compare to dilivar, 993TT material what ever it is and plain oid steel studs.
To me, the real issue here is 2 fold: #1 what is the application as maybe 2 products are needed i.e. turbo an NA (heat expansion rate...) #2 some applications only need a basic? rod HOWEVER, ALL RODS NEED PROPER CLAMPING FORCE SO NUT DOES NOT LOOSTEN AND THE METAL OF STUD IS INTERRELATED TO THIS.
Can you possibly make this an easier topic to understand? (maybe heat is the dividing line i.e. turbo & NA engines??)
Thanks as always...I enjoy learning for you and all on this board!!!!!!
Bob

[Henry Schmidt]

The serrated flange and fine thread both address the loosening issue. Proper torque and a stable platform are necessary for continuous cylinder to head sealing.

As for thermal expansion, you're on your own. I am not an engineer so when we wanted to produce a superior stud we hired a fastener engineer to address the issue. He selected the material based on heat, cylinder materials (of course there was a compromise because of differing cylinder materials) and exposure issues as stated by me and my 30 years of Porsche engine building experience.

Just so we're clear about the purpose of the delivar stud. Porsche was trying to prevent head seepage on cool down that lead to warranty oil leak issues. The stud is not intended to create a stable or even tight seal under operating temperatures.
The CE ring head the same purpose. Hence it's eventual removal then replacement in later big bore engines.

Although some people will have problems with a product and not contact the manufacturer, this is generally not the case in the Porsche world. That said, no one ( not one customer) has contacted me with any complaints about this product. No loose studs, no cylinder sealing issues and or course no failures.

This product is the seventh in a line of development studs and at present we are sold out because we can't keep them on the shelf. Road race teams, import drag , high performance turbo and street DIY customers all enjoy reliable service from these stud kits.

[WERK I]

Originally Posted by Henry Schmidt

Just so we're clear about the purpose of the delivar stud. Porsche was trying to prevent head seepage on cool down that lead to warranty oil leak issues. The stud is not intended to create a stable or even tight seal under operating temperatures.
The CE ring head the same purpose. Hence it's eventual removal then replacement in later big bore engines.

Henry,
Thank you for your continued contributions to the forum. Are you saying the reason for oil seepage from the head/cylinder area was corrected in large bore (greater than 97mm (?)) with the addition of CE rings or other material?